Laminated composite paper



y 1935- G. B. LINDERMAN, JR 2,000,528

LAMINATED COMPOSITE PAPER Filed Dec. 27, 1952 Game)! EZ/mrmaw/k:

Patented May 7, 1935 UNITED STATES 2,000,528 LAMINATED oomosrra PAPERGarrett B. Linderman, Jr., Pittsburgh, Pa assignor to PittsburghEquitable Meter Company, Pittsburgh, Pa., a corporation of PennsylvaniaApplication December 27, 1932, Serial No. 649,082

2 Claims.

This invention relates to laminated composite paper, or a papersubstitute, and more particularly to laminated material composed of alayer or layers of fibrous material, or material manufactured fromfibrous material, and a sheet or sheets of metallic foil all intimatelyunited by adhesion.

The invention resides further in the provision of a high grade papersubstitute made up of laminations, only some of which are made ofmaterials heretofore used in the production of paper of high gradecharacter; and in a uniting of the layers so as to form a structure thatto ordinary inspection appears merely paper of excellent quality.

Papers for general use where durability is of special importance, forexample, paper prepared with ruled markings for business recordsincluding ledger and index paper and blank forms, may be manufactured inaccordance with my invention disclosed herein to meet the need of apaper possessing superior durability and improved quality withoutappreciably increased thickness over that or ordinary paper. Paper usedfor stationery and general correspondence manufactured according to thisinvention will have the appearance of fine quality relatively heavystock, but nlay consist of materials which are relatively cheap.

Heretofore the application of paper to special uses has been hampered bythe lack of necessary and desired properties in the ordinary papers ofcommerce. By my invention special stationery papers may be providedhaving essential properties dictated by the use to which the paper is tobe put. While ordinary paper of commerce may be made from differentsources of fibrous material, with widely differing fillers and manystyles of surface texture and calendering, it has been impossible toproduce a paper impervious to moisture. The paper of my invention may bemanufactured with any desired finish or texture combined with opaquenessand moisture resisting qualities.

It is therefore a primary object of my invention to provide a laminatedcomposite paper, or paper substitute composed of alternate layers offibrous material and metallic foil intimately and uniformly united atall points by an adhesive, so that the resulting composite paper is ineffect a pliable homogenous sheet which may, if desidered, be providedwith a calendered surface or any other typical paper finish.

It is a further object of my invention to produce laminated compositepaper having properties desirable and necessary for a wide variety ofspecial uses that are not possessed by papers heretofore used, though inappearance, upon ordinary inspection, the composite material seems to bepaper.

A further object of this invention is to provide a paper substitute thatmay be used for special purposes to which the ordinary papers ofcommerce known heretofore were either wholly inapplicable or gaveindifierent or unsatisfactory results, to provide a paper substitutethat is impervious to moisture and has the characteristic thata givenarea thereof will not change appreciably in extent with changes fromextremely dry to extremely moist conditions, to the end that the papersubstitute may be used where distances and areas are to be measuredaccurately on its surface because it does not expand or contractappreciably when subjected to conditions that vary from extremely moistto extremely dry, to provide a paper substitute for materials used formaps, charts, accurate drawing paper, and particularly military maps andnavigation charts, which are exposed to widely varying conditions ofrelative humidity and even under these conditions must be relied on torepresent geographical distances to scale so that the location of a shipmay be plotted or ordnance trained by measuring distances to scale onthe chart or map.

The paper of this invention in addition to being substantiallywaterproof and free from. expansion on wetting has a resistant qualitybecause of the metallic layer in the laminated structure, whichminimizes danger of tearing. For these reasons, the paper of myinvention is especially applicable to uses where combinednonexpansibility and resistance to tearing are important such as fortemplates where an edge of the paper is cut to an outline which is to bereproduced by scribing or by other meansfor transferring a facsimile ofthe outline to the metal or other inaterial to be shaped or where theoutline of the template is to be followed by a stylus or pointer tocontrol a reproducing machine. For pattern sheets and rolls providedwith perforations used in controlling machines such as looms and spacingtables for multiple punches, the resistance to tearing andnon-expansible qualities provide a perforated sheet, the perforations ofwhich will not tear or fray and which will maintain their properrelative location in the sheet. Paper stock for color printing whereclose and accurate register of successive superimposed printings isnecessary must, in conjunction with other requirements, be substantiallyfree from distortion. The composite paper of my invention admirablyfulfills this condition.

The valuable feature of maintaining constant area also makes possiblethe use of paper according to this invention as chart paper forrecording meters arid gauges. Recording meters and gauges are generallyinstalled where wide variations in relative humidity are encountered.The records on the charts are traced over a period of time during whichthe quantity of moisture may vary erratically and it would beimpossible, therefore, to correct the readings taken from the chartwithout a simultaneous record of the relative humidity affecting the.chart at the time of recording. Obtaining such a record would be almostimpossible and the endless labor involved and uncertainty of the resultswould make them practically worthless. With the composite paper of myinvention the need for correction for expansion in any direction iseliminated and the record obtained may be taken as indicate of thevariable recorded.

In the preferred embodiments of the invention a valuable feature lies inthe selection of adhesives to adapt the laminated paper to specializeduses, the laminations of the composite paper being joined by theselected adhesive which may include solvents and plasticizers dependingon the contemplated use. .The selection of the adhesive will be governedby the properties desired among which are thermo-plasticity, resistanceto heat and insolubility in liquids. These properties may be varied bythe inclusion of solvents and plasticizers.

Still another object of this invention therefore is to produce alaminated composite paper, the laminations of which are joined uniformlyand at all points by adhesives incorporating solvents and plasticizers,the selection of the adhesive being governed by its properties to suitthe use contemplated.

Documents written on the paper substitute of this invention are immuneto alteration or tampering to a'degree heretofore unattainable as theopaqueness thereof precludes any possibility of tracing signatures orother writing from a copy by means of transmitted light. An adhesivewhich is non-water soluble and unaffected by heat may be selected inwhich solvents may be incorporated if desired to enable the adhesive topenetrate the fibrous layers over the foil to make them moistureresistant and prevent alteration of the fibrous layer bearing theprinting and writing. It is further contemplated in this phase of myinvention to use inks sensitive to heat and/or moisture which willchange in appearance when subjected to heat or concentrated water vaporand also to impregnate the fibrous layer or layers with coloring mattersensitive to heat and/or moisture by direct impregnation of the fibrouslayer or by including it in the adhesive as a solvent and permitting itto penetrate the fibrous layer during manufacture. i

It is therefore a further object of the invention to provide an opaquelaminated composite paper the fibrous laminations of which areimpregnated with a heat sensitive element and the laminated body 'ofwhich is joined uniformly and at all points by a heat resistant binder.

A still further object of this invention is to provide an opaquelaminated composite paper the laminations of which are joined uniformlyand at all points by an adhesive heat resistant binder embodyingsolvents to condition it to initially r penetrate the laminations.

It is desi able that'paper stock for close and accurate or printing befree from distortion so that superimposed successive printings will bein perfect register. Ordinary paper of whatever grade or quality willexpand and contract with changes in moisture content of the air in thepress room, and where the paper stock has been stored prior to use in amoist place contraction of the paper will occur when heat is appliedafter the initial printing to dry the ink in preparation for successiveprintings. This general contraction of the paper is aggravated by localdistortion caused by the wet ink which is applied to the sum face of thepaper at each successive printing an. H

dried by the application of heat.

'In the preferred embodiments of the invention I have provided a paperimmume from general expansion and contraction caused by change inmoisture content and local distortion due to the application and dryingof moist ink. Adhesives may be selected in accordance with the inkdrying process used. Where the ink is dried rapidly by application ofintense heat for very short intervals it is obvious that the adhesiveselected must have heat resistant properties. If moderate dryingtemperatures are used, any adhesive suitable for use in the manufactureof laminated paper, in accordance with the invention, will be suitable.

A still further object of this invention therefore is to produce alaminated composite paper for color printing stock, free from expansionand contraction, the laminations of which are joined uniformly at allpoints by a binder unaflected by ink and ink solvents, and which willremain unchanged at ink drying temperatures.

Ordinary photographically' sensitized papers which are subjected to theaction of chemicals in solution and to fixing and washing liquids aredifficult to handle when wet and frequently tear at some stage of theprocess. The laminated composite paper, or paper substitute of thisinvention with a non-water soluble binder may be provided with aphotographically sensitized surface and is capable of being handledwhile wet without tearing or curling. The distortion-free characteristicenables it to be used. for bearing photographic reproductions which maybe scaled with the assurance that distances measured thereon willrepresent the scale the same distances as measured on the original fromwhich the photographic image is taken. Blueprints and otherreproductions made by contact printing methods or by the photostatprocess will be a true reproduction of the orignal. With a properselection of lenses in accordance with known practice, maps made byaerial photography and reproduced photographically will be more accurateif my com- 1rtiosite paper is used than has been possible heretoore.

Still another object of this invention therefore is to produceanon-curling laminated composite paper free from expansion andcontraction and bearing a photographically sensitized surface, thelaminations of which are joined uniformly and at all points by a binderunaffected by immersion in sensitizing and developing liquids andresistant to temperatures within the range used for drying.

Many industrial processes may be greatly simplified by the use of mycomposite paper and this is particulary true where, during the initialsteps, the paper is subjected to widely .varying temperatures andimmersed in water and solutions of chemicals. Certain specializedprocesses inthefinalstepsrequireathinpaper. Inthia instance the paper ofmy inventiom-is of great utility as during the initial steps of theprocess, it will resist treatment by heat and liquids and may beprepared for the final process by removing all but the desiredlamination, the adhesive being selected to resist separation underconditions imposed by the initial steps of the process, but to permitseparation at the desired stage, for example, by the application ofheat.

Still another object of my invention therefore is to produce a laminatedcomposite paper for use in industrial processes, the laminations ofwhich are joined uniformly and at all points by a binder resistant tointermediate steps of the particular process, but which will permitcertain of the laminations to be separated from the main body thereof.at will, without destruction of the paper substitute.

Further objects of my invention will appear in the following disclosureof the preferred methods of manufacture. and embodiments of my inventionand are defined by the terms of the appended claims.

Figure 1 is a conventional perspective view of one embodiment of mycomposite laminated paper, a portion of the laminated structure beingshown is separated for cleamess of illustration.

Figure 2 is an enlarged fragmentary section through the embodiment ofFigure 1.

Figure 3 is a view similar to Figure 1 illustrating a furtherembodiment.

Figure 4 is an enlarged fragmentary section through the embodiment ofFigure 3.

This application is, in part, a continuation of application Serial No.570,216, in which the invention is disclosed specifically as asubstantially inexpansible recording chart'in combination with arecording meter.

In the preferred forms of my invention, a laminated sheet is producedhaving the pliability and texture of paper. Referring to the drawingthere is shown in each of the severalfigures a portion of a compositesheet, representing by way of specific example, preferred embodiments ofmy invention.

A metallic sheet of the degree of thinness, known as foil, isrepresented by reference character 2. A layer or sheet of paper 3 coversfoil! and is secured thereto in superposed relationship by an adhesiveor binder 4, the thickness of which on the drawing is considerablyexaggerated for the sake of clearness of illustration.

There will hereinafter be described more in detail in connection with adisclosure of the several specific embodiments, binders and adhesivescombined with solvents and plasticizers to make the invention disclosedherein applicable to specific conditions of use.

The adhesive or binder 4, which preferably is one of those disclosed inconnection with the description of the several specific embodiments tofollow, unites a paper layer or layers 3 to foil 2 at all points andwith uniform adhesive power, so that the laminated structure is pliablein all directions and when handled feels like a sheet of ordinary paperof a thickness equivalent to that of the combined thickness of the foiland paper layers. The laminated structure, incorporating the foil isopaque. The foil layer is unaifected by moisture and, therefore, thelaminated structure will not expand or contract with changes of proofand does not lose its toughness on immer-v sion in liquids not solventsof the adhesives.

The modification shown on Figures 1 and 2 of the accompanying drawing iscomposed of two layers or laminations, foil layer 2 and paper sheet 3united in the manner described above by an adhesive 4.

Figures 3 and 4 illustrate the preferred modification in which thelaminated structure has the appearance and feel of paper, and is, ineffect, a paper substitute that may be used to replace ordinary paper.

In this modification, a layer of foil 2 is concealed between two layersor sheets 3 of paper. The adhesive indicated by reference character 4unites layer 3 uniformly and at all points to foil 2. The laminatedstructure just described, because of the flexible character of adhesive4, which is present in an amount just sufficient to intimately unitelayer 3 to foil 2 without forming a perceptible body or layer ofadhesive, is pliable in all directions, and constitutes a unitarystructure.

The layer of foil concealed by the paper imparts aquality which presentsto the sense of touch the feel of a fine paper of the heavier and moreexpensive grades.

The composite structure of Figures 1 and 2 is pliable and may be usedwhere a paper substitute is desired, having one side which presents theappearance of metallic foil.

For the fibrous portion of my laminated composite structure, paper ofany kind or quality may be used. Preferably the quality and surfacefinish of the paper will be selected in accordance with the use which iscontemplated in each instance for the laminated paper. In producingpaper which is to form a part of my laminated paper substitute, in eventthat a special surface finish of the paper is desired, it is necessaryto treat one side only of each layer which is to enter the finishedproduct.

Any desired weight or thickness of paper may be used but paper of fromone one-thousandth of an inch to four one-thousandths of an inchthickness is preferable, and if paper is selected within these limits ofthickness, the resulting composite structure will present the appearanceof paper and will be applicable as a substitute for ordinary paper.

For the impervious moisture resisting component of my paper substitute,I prefer to use aluminum foil. I have discovered that aluminum foil whenunited with paper according to the invention disclosed herein, gives asa result a laminated structure which is tough, pliable and but slightlyheavier than ordinary paper, which it resembles. It is to be understoodthat aluminum foil of any desired thickness may compose the opaqueandimpervious component of the laminated paper of this invention,'but Ihave discovered that foil of the thickness between the limits of threeand one-half ten-thousandths of an inch to one one-thousandth of an inchis best suited to the production of my laminated paper substitute.

The adhesive material for joining the paper to the foil layer ispreferably a special thermoplastic adhesive which I have found to beespecially suitable where high adhesive properties are desirable. Thisthermoplastic adhesive permits the laminations to be separated at agiven time, as, for example, when in the course of an industrialprocess, it is necessary to use an embodiment of the paper-like materialof this invention, which may be separated into its componentlaminations' during an intermediate or final step in the process. Rubberlatex also has high adhesive properties and permits separation uponheating.

Where heat-resistant properties of the adhesive are desirable. theadhesive bond between the fibrous material and the foil may be effectedby using a formaldehyde urea resin reacted in the recent resin stage, ora stage B glyptal resin combined with plasticizers and solvents toproduce a glue. These resins when used as a binder to unite thelaminations. produce a paper substitute, the structural unity of whichwill not be disturbed by the later application of heat.

The paper-llkequalities of the laminated paper substitute of thisinvention make it applicable to general paper uses, the quality ofdurability and imperviousness to moisture impartedto it by the metallicfoil component enables it to replace papers generally and its specialqualities open up new fields of use to which ordinary paper wasimperfectly suited.

The adhesives disclosed herein, which are insoluble in water when usedto join the component layers of my paper, give, as a result, a paperwhich is completely waterproof.

It will be understood by those skilled in the art that all of thecommercially available adhesives including, organic and inorganiccements, natural and artificial latex, animal and vegetable glues, eventhose that develop their adhesive properties by evaporation of volatilesolvents may be employed where the adhesive has the desired propertiesto adapt it to the particular use, as for example for uses wherein theevaporation and absorption of the solvent is of little consequence or isbeneficial to the resulting composite structure.

The preferred thermo-plastic cement is not dependent upon solventevaporation for developing adhesion between two surfaces. The intimatebond between the component layers of the composite structure provided bythe cement is secured by means of heat and pressure alone, the volatilesolvents serving only to lay a film on the surface and are preferablyentirely volatilized prior to joining the surfaces. This adhesive whenin solution is light in .color and deposits a clear, nearly colorlessfilm. It is waterproof and has excellent flexibility and adhesion over awide range of temperatures. A suitable thermoplastic cement suitable forthe purposes of the present invention is sold commercially by the E. I.du Pont de Nemours & Company, known as Thermoplastic Cement #4620.

In adhesively joining the component laminations of the compositelaminated paper. the heat necessary to secure a firm union need beapplied only momentarily, thus permitting a rapid and continuousproduction of the laminated paper. The time of application of the heatmay vary, depending on the heat conductivity of the laminated\structure. Temperatures of from 100 to 150 C. and low pressures may beemployed to secure perfect union, although pressures of from 200 to 300pounds per square inch are preferred.

Latex, preferably artificially prepared, gives an intimate bond betweenthe paper and the foil, which is not aifected by moisture and is firmlyadherent. Preferably, the latex adhesive used contains aboutthirty-eight percent solids. but the invention is not limited to thiscomposition of latex. Preferably also the latex is applied to the paperor foil, which then are brought together and pressed between rolls. noheat being employed for this purpose. although heat may be used in somecases. In this way an excellent bond is obtained.

The paper substitute of my invention with the laminations thereof unitedby rubber latex or the thermo-plastic adhesive is suitable for any paperuse. Because of its wholly new qualities of opaqueness, imperviousnessto moisture, and its further desirable property. of being undistorted inthe presence of water vapor in concentrated amounts, it may be used formany special purposes. Stationery; wrapping paper, and accuratephotographic, drawing and chart papers are exemplary of uses in a widefield of applicability to which the paper of my invention furnishes anew product.

The paper substitute of the foregoing disclosure is, because of specialproperties inherent in the structure thereof, a safety paper. Itsinability to transmit light prevents tracing of signature or otherinscription by transmitted illumination, which is a common method offorging or tracing documents. To detect attempts to falsify inscriptionson the surface of the laminated paper by separating the layers so thatlight may be passed through one component thereof, it is contemplated touse heat sensitive ink in preparing the original and genuine inscriptionso that if heat be "applied to separate the layers, this fact will beshown by alteration in the appearance of the ink of the genuineinscription.

Genuine documents written on the safety paper provided by this inventionwill preclude the copying of the signature or any part of theinscription on ordinary paper by transmitted light. A double safeguardis thus provided since if the original is inscribed on the safety paperof this invention, a falsified copy thereof must be attempted on a likesheet so that two layers of foil intervene to frustrate any productionof a copy. Clear evidence of tampering would appear on both copies.

The light excluding properties of aluminum are such that it is opaque toradiant energy, which is perceptible to the sense of sight. Special raysare therefore ineffectual to transmit sufilcient illumination to makepossible the copying of an inscription to or from my safety paper.

To make tampering impossible and, therefore. enhance the safety papervalue of the invention, I preferably Join the foil and paper layers witha synthetic resin, as previously described, incorporating solvents andplasticizers .which when used as an adhesive will resist separation ofthe layers at any temperature which may be applied to the laminatedstructure without destroying it. This further inherent property of thepaper substitute of this invention makes tampering impossible, andtherefore an additional means. such as colored ink, to detect anattempted alteration is unnecessary. In this latter embodiment of thepaper substitute wherein a synthetic resin is used, heating will morefirmly unite the components of the laminated sheet.

In the manufacture of the novel product herein disclosed, it is producedcontinuously when joined with the preferred thermoplastic cement. Thecement may be applied to either the paper or the metallic layerindiii'erently. The paper is then rolled in contact with the aluminumfoil between two polished steel rollers which are heated by any suitablemeans to approximately 180 F. or between rubber rollers. The pressureapplied to the rollers may vary within wide limits. If heavy pressuresare used, lower temperatures may be maintained at the rollers, andconversely if lighter pressures are used, the rollers should be kept ata higher temperature. The thermoplastic adhesive referred to above, whenused for uniting the layers if preferably applied to the surfaces of thefoil, allowing sumcient time to elapse to permit evaporation of all ofthe solvent, after which it is joined by heat and pressure appliedwithin the limits previously disclosed. These operations may be formedcontinuously, the foil layer receiving the adhesive coating as itismovedtowardtheheated rolls. The time and/or distance of passage from thepoint of application of the adhesive to the rolls may be regulated toallow time for evaporation of the solvents.

The invention maybe embodied inother specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are there-.

2. A laminated composite stationery papersuitable for taking aninscription consisting of a layer of metallic foil adhesively secured byunvulcanized latex to external sheets of paper of writing paper quality.

GARRETT B. LmDERMAN, Jr.

